Flame position control electrodes

ABSTRACT

A method and apparatus for stabilizing a flame in a combustion volume is disclosed. The present method and device may include a burner nozzle configured to support the flame, a halo electrode configured to anchor the flame, and electrodes disposed in top and bottom regions of the flame configured to apply voltage difference above or below the halo electrode that may assist in anchoring of the flame to the halo electrode while also controlling a shape and position of the flame. Effects of different electrical configurations within the combustion volume for stabilizing the flame are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority benefit from U.S. ProvisionalPatent Application No. 62/010,931, entitled “FLAME POSITION CONTROLELECTRODES”, filed Jun. 11, 2014; which, to the extent not inconsistentwith the disclosure herein, is incorporated by reference.

BACKGROUND Technical Field

The present disclosure relates generally to combustion systems, and moreparticularly, to electrical configurations for stabilizing a flameposition within a combustion volume.

SUMMARY

Methods and devices for stabilizing a flame provided by combustion of afuel and an oxidizer within a combustion volume may include a burnernozzle supporting the flame, and one or more electrodes configured toelectrically communicate with one or more voltage power sources. Theflame may additionally be charged by different methods for allowinginteraction with electrical charges that may be applied within thecombustion volume for better flame stabilization.

According to various embodiments, a halo electrode may include anapplied voltage potential configured to charge the halo electrode, andinclude additional applied voltage potentials configured to charge oneor more electrodes disposed above or below the charged halo electrodeand may be configured to improve flame stability by attaching oranchoring the flame to the halo electrode and thereby maintaining theflame in a suitable shape and position. Different electricalconfigurations may be employed for the application of the voltagepotentials.

According to an embodiment, a suitable voltage source, such as a DC oran AC low-voltage power source or a DC or an AC high-voltage powersource, may apply a voltage potential to the halo electrode to create anelectric field that may interact with the flame to attach or anchor theflame to the halo electrode. Additionally, another voltage source mayapply a voltage potential to a top electrode disposed above the haloelectrode configured to create a voltage difference between the topelectrode and the halo electrode. Such an arrangement may create anelectric current that may assist in keeping the flame attached oranchored to the halo electrode. Furthermore, sensors located in variousparts of the combustion volume may be configured to detect movements inthe flame and may be further configured to send signals to switches andcontrollers for application of voltage potentials to either or bothelectrodes, respectively, for keeping the flame in a desired position.Other embodiments may further include combinations of one or moreelectrodes disposed above and/or below the flame configured to providefor better flame stabilization.

According to another embodiment, the top electrode again may bepositioned above the halo electrode and configured to charge the flame.A first resistor may be operatively coupled between the halo electrodeand a bottom electrode positioned below the halo electrode and a secondresistor may be operatively coupled between the bottom electrode and theburner nozzle, wherein the burner nozzle is itself operatively coupledto a ground potential. When the flame makes contact with the haloelectrode, a current may flow across the first resistor and secondresistor producing voltage drops proportional to the current beingpassed through the respective resistors that may allow the flame tobetter attach or anchor to the halo electrode. The halo electrode andresistor may also be combined by coating the halo electrode with aceramic or otherwise electrically resistive coating applied to itssurface or otherwise at least partially in series with the electricallyconductive path.

BRIEF DESCRIPTION OF DRAWINGS

Various, non-limiting embodiments are disclosed and described by way ofexample with reference to the accompanying figures. The figures areschematic and are not intended to be drawn to scale. Unless indicated asrepresenting the background art, the figures represent aspects of thedisclosure.

FIGS. 1A and 1B are intended to show a velocity distribution of a fuelstream exiting a burner nozzle and passing through a surrounding ambientatmosphere and the respective shape of a flame within a combustionvolume, according to an embodiment.

FIG. 2 shows an application of a first voltage potential to a haloelectrode disposed above a burner nozzle, according to an embodiment.

FIG. 3 depicts an application of a second voltage potential to a secondelectrode disposed above the halo electrode of FIG. 2, according to anembodiment.

FIG. 4 depicts an application of a voltage third potential to a thirdelectrode disposed below the halo electrode of FIG. 2, according to anembodiment.

FIG. 5 depicts an application of voltage potentials to a secondelectrode disposed above and a third electrode disposed below the haloelectrode of FIG. 2, according to an embodiment.

FIG. 6 shows the application of voltage potentials to the halo electrodeand the control of the flame position by connection of resistors belowthe halo electrode between the halo electrode and a third electrode andbetween the burner and the third electrode, according to an embodiment.

FIG. 7 shows application of voltage potentials to the halo electrode andto a second halo electrode disposed in and surrounding the top portionof the flame above the first halo electrode, according to an embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise.

Other embodiments may be used and/or other changes may be made withoutdeparting from the spirit or scope of the disclosure.

Problems in combustion systems due to instabilities in flame positionand shape may be caused in part by high, subsonic, or even supersonicspeeds of fuel being injected into a combustion volume. High fuelinjection speeds may result in a non-uniform fuel distribution and anunstable flame within the combustion volume, which may cause problemssuch as poor combustion, increased emissions of pollutants, flashback,poor heat transfer, reduced component life, and system damage, amongstothers.

Embodiments are disclosed that include methods and devices for theapplication of voltage potentials proximate to a flame within acombustion volume for improving flame position stabilization. Thepresent disclosure is described in detail with reference to embodimentsillustrated in the drawings, which form a part hereof. In the drawings,which are not necessarily to scale or to proportion, similar symbolstypically identify similar components, unless context dictatesotherwise. Other embodiments may be used and/or other changes may bemade without departing from the spirit or scope of the presentdisclosure. The illustrative embodiments described in the detaileddescription are not meant to be limiting of the subject matter presentedherein.

As used herein, the following terms may have the following definitions:

“Halo electrode” refers to a conducting material in a circumferentialshape such as a ring, a toroid, or an annulus configured for theapplication of an electric charge, a voltage potential, and/or anelectric field proximate to a flame. The halo electrode may be unbroken(continuously circumferential to the flame with no cut) or may beembodied as one or more sections having an air gap. The halo electrodeand a resistance may optionally be combined by means of a ceramic orotherwise electrically resistive coating applied to the halo electrodeor otherwise partially or wholly in series with the electricallyconductive path.

“Anchoring” refers to maintaining a flame position relative to a solidsurface such as the halo electrode, in such a way that the anchoredregion of the flame stays proximate to the solid surface.

FIG. 1A is a diagram showing a fuel flow velocity V1, V2, V3distribution and flame 106 (shown in FIG. 1B) within a combustion volume102, which may include a burner nozzle 104 configured to support a flame106 (shown in FIG. 1B), according to an embodiment. Also shown is thedistribution of fuel 108 being injected from the burner nozzle 104 intothe combustion volume 102. Accordingly, the closer the fuel 108 is tothe burner nozzle 104, the higher fuel flow velocity is, thus flowvelocity V1 may be greater than flow velocity V2 and flow velocity V2may be greater than flow velocity V3 (i.e., V1>V2>V3). The combustionvolume 102 may be, for example, part of a boiler, a water tube boiler, afire tube boiler, a hot water tank, a furnace, an oven, a flue, a cooktop, or another system employing the combustion volume 102. Not shown isa source of an oxidizer supporting combustion of the fuel 108. Theoxidizer may include ambient air into which the fuel stream exits or itmay include a separate flow of oxidizer materials, such as oxygenconcentrated air, oxygen, ozone, hydrogen peroxide, recycled flue gases,or combinations thereof, injected directly into the fuel flow stream.

FIG. 1B shows an idealized behavior of a flame 106 according to thedistribution of fuel flow velocities V1, V2, V3. Fuel flow velocitiesV1, V2, V3 may range from subsonic to supersonic, making control of theflame 106 more difficult in the areas closer to the burner nozzle 104.Accordingly, the flame 106 may be more easily controlled in region V3than in region V2 and more easily controlled in region V2 than in regionV1. If no control system is applied in the combustion volume 102,different factors such as heat requirement variations, weather, andcomponent wear or damage, among others, may affect the shape andstability of flame 106.

The flame 106 may include a variety of charged and uncharged particlesand molecules. The volume of charged particles may include electrons110, positive ions 112, negative ions, positively and negatively chargedparticles, such as charged and uncharged fuel vapor, and charged anduncharged combustion products, unburned fuel 108, and air. The volume ofcharged particles may be distributed in various locations of combustionvolume 102 at different times during the combustion process.

Because of rapid transient behavior, the flame 106 may need to becontrolled at every instant to prevent the flame 106 from contact withobjects or components or combustion equipment within the combustionvolume 102, in order to avoid potential damages due to thermal effects.During any of such possible events, power may be removed or applied toelectrodes in the combustion volume 102 through one or more switchesand/or control circuits attached to the power source, to repel orattract the flame 106. These electrodes may include different shapes andtypes and may be arranged in different configurations within thecombustion volume 102.

A halo electrode along with the application of voltage potentials aboveor below the halo electrode may improve flame stability by anchoring theflame 106 and keeping the flame 106 in a suitable, stable position.

FIG. 2 depicts an embodiment configured to provide an application of avoltage potential to a halo electrode 202 within a combustion volume102. Accordingly, the halo electrode 202 may be located in differentareas above a burner nozzle 104, such as proximate to V3, where fuelflow velocity may be lower and a flame 106 may be more easilycontrolled, as shown in FIGS. 1A and 1B. The halo electrode 202 mayexhibit a diameter D ranging from about 1 cm to about 10 cm, dependingon intended use, and have a center axis of rotation lying on or aboutcoincident with a longitudinal axis A of the burner nozzle 104. The haloelectrode 202 may be made of different suitable high temperature,corrosion resistant conductive materials, including, for example,silver, copper, gold, tungsten, nickel, iron, platinum, tin, and alloysthereof. The halo electrode 202 may be used for anchoring the flame 106,improving flame stability. The flame 106 may or may not touch the haloelectrode 202. Additionally, the flame 106 may be charged by differentmethods, such as connecting a voltage power source to the burner nozzle104, or connecting a voltage power source to electrodes in differentareas near the flame 106 along the flame length, or to the haloelectrode 202, e.g., a first high-voltage power supply (HVPS1) 204.Charging the flame 106 may allow for a better electrical control of theflame 106, allowing for modifications of the shape and position of theflame 106.

Any suitable voltage source, such as a first DC or an AC low-voltagepower source or a first DC or an AC high-voltage power supply such asHVPS1 204, may be configured to apply a voltage potential to the haloelectrode 202, which may create an electric field proximate to the haloelectrode 202 that may interact with charged particles included in theflame 106. For example, if the flame 106 carries a positive charge andthe halo electrode 202 carries a negative charge, the electric field mayattract positive ions 112 of the flame 106 helping to attach or anchorthe flame 106 to the halo electrode 202.

The electric field may include one or more DC electric fields, one ormore AC electric fields, one or more pulse trains, one or moretime-varying waveforms, one or more digitally synthesized waveforms,and/or one or more analog waveforms, or combinations thereof.

Generally, when describing embodiments employing voltage power sources,sensors may also be included in different parts of the combustion volume102 and configured for detecting movement in the flame 106 and sendingsignals to switches and controllers operatively coupled to thehigh-voltage power sources, which may apply voltages to one or moreadditional electrodes for attracting or repelling the flame 106 in orderto maintain the flame 106 at a suitable, stable shape and position. Thedifferent voltage potentials may also charge the flame 106. For example,sensors may be operatively coupled to the halo electrode 202 and maythen send signals to switches and controllers for the first high-voltagepower supply HVPS1 204 to initiate or change the voltage potentialsapplied to the halo electrode 202.

FIG. 3 shows another embodiment configured to control an application ofvoltage potentials, through one or more switches and/or controlcircuits, by first and second high-voltage power supplies HVPS1 204 andHVPS2 304, respectively, to a halo electrode 202, and to a secondelectrode 302 located above a flame 106, within a combustion volume 102.

According to various embodiments, a first voltage potential may beapplied by the first high-voltage power supply HVPS1 204 to the haloelectrode 202 and a second voltage potential may be applied by thesecond high-voltage power supply HVPS2 304 to the second electrode 302.For example, this arrangement can be especially advantageous forcreating an electrical field along the flame 106 to maintain a suitableflame shape and position. For example, if the halo electrode 202 is at adifferent (e.g., lower) potential than the second electrode 302 (at ahigher potential), then a voltage difference (V_(E2)-V_(E1)) betweenoutputs of the first and second high-voltage power supplies HVPS1 andHVPS2 can generate a movement or a flow of charges within the flame 106between the first and second potentials (e.g. parallel or antiparallelto current, depending on polarity). The arrangement of FIG. 3 maythereby drive an electric current, I, that attracts the flame 106 formore stable anchoring on or near the halo electrode 202. Other chargecombinations, levels, and polarities are possible for attracting orrepelling the flame 106, which may depend on flame position andbehavior. In experiments, the inventors found either or both (AC)polarities can cause enhanced flame anchoring. Some experiments impliedthat supplying a positive polarity on HVPS2 (relative to HVPS1), in anotherwise electrically isolated system, may tend to have a strongerrelative anchoring effect than the opposite polarity.

FIG. 4 depicts an additional embodiment configured to provide anapplication of voltage potentials below a halo electrode 202 within acombustion volume 102, in which a second electrode 402 may be charged bya second high-voltage power supply HVPS2 404. Accordingly, differentvoltage potentials may be applied through one or more switches and/orcontrol circuits by a first high-voltage power supply HVPS1 204 to thehalo electrode 202, and by the second high-voltage power supply HVPS2404 to the second electrode 402 to create a voltage difference(V_(E1)-V_(E3)). For example, if the second electrode 402 is at a lowerpotential than the halo electrode 202, the voltage difference betweenthe first and second high-voltage power supplies HVPS1 204 and HVPS2404, can, again, generate a charge flow in the flame 106 creating anelectric current, I, that may drag down the flame 106 and may assist inkeeping the flame 106 anchored at or slightly below the halo electrode202. Other charge combinations, levels, and polarities are possible forattracting or repelling the flame 106, which may depend on flameposition and behavior.

FIG. 5 depicts another embodiment configured to provide an applicationof respective selected voltage potentials above and below a haloelectrode 202 within a combustion volume 102. The halo electrode 202 maybe operatively coupled to a first high-voltage power supply HVPS1 204, asecond electrode 302 disposed above the halo electrode 202 may beoperatively coupled to a second high-voltage power supply HVPS2 304, anda third electrode 402 disposed below the halo electrode 202 may beoperatively coupled to a third high-voltage power supply HVPS3 404. Eachpower source can be controlled through one or more switches and/orcontrol circuits. Different voltage levels and/or polarities may beapplied to the halo electrode 202, second electrode 302, and thirdelectrode 402 for suitable flame stabilization, flame modulation, orother desirable effects.

FIG. 6 depicts another embodiment configured to provide an applicationof voltage potentials within a combustion volume 102, in which a secondelectrode 302, powered by a first high-voltage power supply HVPS1 304controlled through one or more switches and/or control circuits, maycharge a flame 106. A first resistor (R1) may be operatively coupledbetween the halo electrode 202 and a third electrode 402, neither ofwhich includes a high-voltage power supply. A second resistor (R2) maybe operatively coupled between the third electrode 402 and the burnernozzle 104, wherein the burner nozzle 104 is operatively coupled to acircuit ground 602. The resistors, R1 and R2, may have different values.When the flame 106 makes contact with the halo electrode 202, a current,I, may flow across the first and second resistors R1 and R2, producing avoltage drop equal to current times the total resistance(V_(A)=I(R1+R2)), establishing a first voltage potential (V_(A)) at thehalo electrode 202, with respect to the ground potential at the circuitground 602. The voltage drop produced across the first and secondresistors R1 and R2 may allow the flame 106 to be more effectivelyanchored to the halo electrode 202.

A second voltage potential (V_(B)) at the third electrode 402—relativeto the ground potential—is equal to the voltage drop across the secondresistor R2, i.e., current times the second resistance (V_(B)=I·R2). Inaccordance with very well-known principles, the ratio of the secondvoltage potential V_(B) at the third electrode 402 to the first voltagepotential V_(A) at the halo electrode is equal to the ratio of thesecond resistance R2 to the total resistance

$\left( {V_{B} = {\frac{R\; 2}{{R\; 1} + {R\; 2}} \cdot V_{A}}} \right).$

Thus, for a given first voltage potential V_(A) at the halo electrode202, the value of the second voltage potential V_(B) at the thirdelectrode 402 can be varied by varying the relative values of the firstand second resistors R1, R2 provided the total resistance R1+R2 remainsthe same.

As described above, a first series circuit may be established betweenthe high-voltage power supply HVPS1 304 and the circuit ground 602 viathe second electrode 302, the flame 106, the halo electrode 202, and thefirst and second resistors R1, R2.

At the same time, however, a second series circuit may be establishedbetween the halo electrode 202 and the circuit ground 602 via the fuelstream 108 and the burner nozzle 102. The second series circuit iselectrically parallel to the portion of the first series circuitextending between the halo electrode 202 and the circuit ground 602 viathe first and second resistors R1, R2. Alternatively, where there islittle or no electrical current flow in the fuel stream 108, anelectrical field may be established by the voltage difference betweenfirst voltage potential V_(A), at the halo electrode 202, and groundpotential, at the burner nozzle 104. Finally, in embodiments thatinclude the third electrode 402, a voltage distribution within anelectric field established across the fuel stream 108 can be controlledby selection of the value of the second voltage potential V_(B), at thethird electrode 402. The value of the second voltage potential V_(B)can, in turn, be determined by selection of the relative values of thefirst and second resistors R1, R2, as explained above.

FIG. 7 depicts another embodiment configured to provide an applicationof voltage potentials to a first halo electrode 202 and to a second haloelectrode 702 configured to further control a flame 106. Anchoring mayresult when the first halo electrode 202 is operatively coupled throughone or more switches and/or control circuits to a first high-voltagepower supply HVPS1 204 while a second halo electrode 702 is operativelycoupled through one or more switches and/or control circuits to a secondhigh-voltage power supply HVPS2 304 such that, if the first haloelectrode 202 is at a lower potential than the second halo electrode702, then a voltage difference (V_(E2)-V_(E1)) between the first andsecond high-voltage power supplies HVPS1 and HVPS2 again generates acharge flow (current, I) toward the lower potential that may drag downthe flame 106 for more stable anchoring on the first halo electrode 202.In other embodiments other shapes, positions, and combinations ofelectrodes may be considered for an efficient anchoring of the flame 106within the combustion volume 102.

Ordinal numbers, e.g., first, second, third, etc., are used in theclaims according to conventional claim practice, i.e., for the purposeof clearly distinguishing between claimed elements or features thereof.The use of such numbers does not suggest any other relationship, e.g.,order of operation, relative position of such elements, etc.Furthermore, an ordinal number used to refer to an element in the claimsdoes not necessarily correlate to a number used in the specification torefer to an element of a disclosed embodiment on which those claimsread, nor to numbers used in unrelated claims to designate similarelements or features.

Where a claim limitation recites a structure as a grammatical object ofthe limitation, that structure itself is not an element of the claim,but is a modifier of the subject. For example, in a hypotheticallimitation that recites “a burner nozzle configured to emit a flowstream and to support a flame within the flow stream,” the flow streamis not an element of the claim (nor is the flame), but instead serves tohelp define the scope of the term burner nozzle. Additionally,subsequent limitations or claims that recite or characterize additionalelements relative to the flow stream do not render the flow stream anelement of the claim. Only where the flow stream itself is recited asthe grammatical subject of a claim limitation does it become anessential element of the claim.

The abstract of the present disclosure is provided as a brief outline ofsome of the principles of the invention according to one embodiment, andis not intended as a complete or definitive description of anyembodiment thereof, nor should it be relied upon to define terms used inthe specification or claims. The abstract does not limit the scope ofthe claims.

Finally, while various aspects and embodiments have been disclosedherein, other aspects and embodiments are contemplated. The variousaspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

What is claimed is:
 1. A combustion system, comprising: a burner nozzle having a longitudinal axis, positioned within a combustion volume and configured to emit a flow stream, including a mixture of fuel and oxidizer, that expands and slows at distances receding away from the burner nozzle, and to support a flame via the flow stream; a first high-voltage power supply (HVPS); and a first electrode operatively coupled to the first HVPS, the first electrode being configured and disposed on a diameter generally concentric with the longitudinal axis of the burner nozzle at a first distance from the burner nozzle, the first distance corresponding to a region in which the flow stream has expanded and marginally slowed, the first HVPS being configured to supply a first voltage potential to the first electrode, sufficient to charge the flame such that the charged flame is stably held on or near a surface of the first electrode.
 2. The combustion system of claim 1, wherein the first electrode has a ring torus shape disposed in a plane and having a center axis of rotation normal to the plane, wherein the center axis of rotation is about coincident with the longitudinal axis of the burner nozzle.
 3. The combustion system of claim 2, comprising an electrically resistive coating on the surface of the first electrode.
 4. The combustion system of claim 2, further including one or more additional electrodes, each operatively coupled to a respective additional HVPS.
 5. The combustion system of claim 4, wherein the one or more additional electrodes include a second electrode disposed a second distance from the burner nozzle, greater than the first distance and corresponding to a top region of the charged flame.
 6. The combustion system of claim 5, wherein the second electrode has a ring torus shape disposed on a diameter generally concentric with the longitudinal axis of the burner nozzle.
 7. The combustion system of claim 5, wherein the second electrode is configured to receive a second voltage potential, different from the first voltage potential from the respective additional HVPS of the second electrode, and thereby producing an electrical field along a length of the charged flame between the first electrode and the second electrode.
 8. The combustion system of claim 5, wherein the one or more additional electrodes include a third electrode disposed a third distance from the burner nozzle, less than the first distance and corresponding to a base region of the charged flame, the additional respective HVPS of the third electrode being configured to provide a third voltage potential to the third electrode, and to produce thereby a voltage difference between the first electrode and the third electrode.
 9. The combustion system of claim 8, wherein the first, second, and third voltage potentials are selected to produce voltage differences between each of the first, second, and third electrodes.
 10. The combustion system of claim 5, wherein the one or more additional electrodes comprise a second electrode disposed a second distance from the burner nozzle, less than the first distance and corresponding to a base region of the charged flame.
 11. The combustion system of claim 6, wherein each of the first and the one or more additional electrodes further includes a switch for independently opening and closing electrical continuity between the first and the one or more additional electrodes and the respective additional HVPS.
 12. The combustion system of claim 1, wherein the oxidizer is selected from the group consisting of oxygen in ambient air, oxygen concentrated air, oxygen, ozone, hydrogen peroxide, recycled flue gases and combinations thereof.
 13. The combustion system of claim 1, wherein the oxidizer is oxygen from ambient air.
 14. A combustion system, comprising: a burner nozzle having a longitudinal axis and configured to emit a flow stream including a mixture of fuel and oxidizer within a combustion volume, the burner nozzle being electrically coupled to a circuit ground; a first electrode disposed a first distance from the burner nozzle corresponding to a top region of flame supported by the flow stream emitted by the burner nozzle; a high-voltage power supply (HVPS) operatively coupled to the first electrode and configured to supply a first voltage potential to the first electrode; a second electrode having a ring torus shape lying in a plane and having a center axis of rotation normal to the plane and about coincident with the longitudinal axis of the burner nozzle, the second electrode being disposed a second distance, less than the first distance, from the burner nozzle; an electrical resistance operatively coupled between the second electrode and the burner nozzle, a series circuit being established between the HVPS and the circuit ground, via the first electrode, the flame, the second electrode, the electrical resistance, and the burner nozzle, the series circuit being configured to establish a second voltage potential at the second electrode on the basis of a current flowing in the circuit and the resistive value of the electrical resistance.
 15. The combustion system of claim 14, comprising a third electrode disposed a third distance, less than the second distance, from the burner nozzle, and wherein: the electrical resistance comprises a first resistor operatively coupled between the second electrode and the third electrode, and a second resistor operatively coupled between the third electrode and the burner nozzle; and the series circuit is configured to establish the second voltage potential at the second electrode on the basis of the current flowing in the circuit and a sum of the resistive values of the first and second resistors; and the series circuit is further configured to establish a third voltage potential at the third electrode on the basis of the current flowing in the circuit and the resistive value of the second resistor.
 16. A method for stably positioning a flame within a combustion volume, comprising the steps of: supporting a flame within a combustion volume by emitting into the combustion volume a flow stream, including a mixture of fuel and oxidizer, from a burner nozzle; and operating a first high-voltage power supply (HVPS) to generate a first voltage potential; and holding the flame to a first electrode by applying the first voltage potential to the flame and electrically attracting the flame to the first electrode.
 17. The method of claim 16, wherein the applying the first voltage potential to the flame and electrically attracting the flame to the first electrode comprises applying the first voltage potential to the first electrode.
 18. The method of claim 16, wherein the holding the flame to a first electrode comprises holding the flame to a first electrode having a ring torus shape disposed in a plane and having a center axis of rotation normal to the plane and about coincident with an axis of the burner nozzle.
 19. The method of claim 16, wherein the applying the first voltage potential to the flame and electrically attracting the flame to the first electrode comprises: applying the first voltage potential to a first electrode positioned a first distance from the nozzle; and applying a second voltage potential, different from the first voltage potential, to a second electrode positioned a second distance, different than the first distance, from the burner nozzle.
 20. The method of claim 19, wherein the applying a second voltage potential to a second electrode comprises applying the second voltage potential to a second electrode having a ring torus shape, disposed on a diameter generally concentric with an axis of the burner nozzle.
 21. The method of claim 19, wherein the applying a second voltage potential to a second electrode positioned a second distance from the burner nozzle comprises applying the second voltage potential to the second electrode positioned a second distance, less than the first distance, from the nozzle.
 22. The method of claim 19, wherein: the applying the first voltage potential to a first electrode comprises closing a switch operatively coupled between a first voltage source and the first electrode; and the applying a second voltage potential to a second electrode comprises closing a second switch operatively coupled between a second voltage source and the second electrode.
 23. The method of claim 19, wherein the applying a second voltage potential to a second electrode positioned a second distance from the burner nozzle comprises applying the second voltage potential to the second electrode positioned a second distance, greater than the first distance, from the nozzle.
 24. The method of claim 23, comprising: applying a third voltage potential to a third electrode positioned a third distance, less than the first distance, from the nozzle.
 25. The method of claim 16, wherein the first electrode is positioned a first distance from the nozzle, and wherein applying the first voltage potential to the flame and electrically attracting the flame to the first electrode comprises: applying the first voltage potential to a second electrode positioned a second distance, greater than the first distance, from the nozzle; passing a first electrical current from the second electrode through the flame to the first electrode, and from the first electrode through an electrical resistance to a circuit ground; and holding the burner at a ground potential.
 26. The method of claim 25, comprising passing a second electrical current from the first electrode through the flow stream to the burner nozzle.
 27. The method of claim 25, comprising establishing an electrical field along the flow stream between the first electrode and the burner nozzle.
 28. The method of claim 27, wherein the electrical resistance comprises first and second series resistors, the method comprising controlling a voltage potential at a third electrode positioned between the first electrode and the burner nozzle and electrically coupled to a node between the first and second series resistors by selecting relative resistance values of the first and second series resistors. 